Bright and Stable Alloy Core/Multishell Quantum Dots

摘要

Quantum dots (QDs) have been considered as an excellent light-emitting material for next-generation displays because of their high quantum efficiency (QE), broad absorption, highly saturated color, and simple color tunability. The synthetic methods to prepare high-quality QDs in a colloidal phase have been continuously developed, and it has been proposed that the advantages of the QDs can be practically realized in various optoelectronic devices in the near future. In particular, red-light-emitting CdSe-based QDs have been significantly optimized in terms of emission wavelengths, QE, and tolerance against fabrication conditions such as high-temperature curing or chemical treatments. The red-light-emitting QDs showed great potential as color converting phosphor for white-light-emitting diodes (LEDs) to improve the average color rendering index (R_a) up to 90, which is a quality standard for general illuminations. The electroluminescent device employing red QDs as an active fluorophore, which endure a thiol cross-link process to increase the packing density, showed high brightness of 12380 cdm~(-12) and external QE (EQE) of 2.1 LmW~(-1). However, the QE and stability diminish rapidly as the size of QDs is reduced, because the density of the surface defects are more easily generated by a large surface-to-volume ratio and the steric hindrance of the capping ligands.